Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, robustness, lower operating costs, and many others. LEDs are particularly suitable for applications requiring low-profile light fixtures. The LEDs' smaller size, long operating life, low energy consumption, and durability make them a great choice when space is at a premium. For example, LED-based linear fixtures can be configured as floodlight luminaires for interior or exterior applications, providing wall-washing or wall-grazing lighting effects for architectural surfaces and improving definition of three-dimensional objects.
In particular, luminaires employing high-flux LEDs are fast emerging as a superior alternative to conventional light fixtures because of their higher overall luminous efficacy and ability to generate various light patterns. However, one significant concern in the design and operation of these luminaires is thermal management, because high-flux LEDs are sensitive to heat generated during operation. Maintaining optimal junction temperature is an important component to developing an efficient lighting system, as the LEDs perform with a higher efficacy and last longer when run at cooler temperatures. The use of active cooling via fans and other mechanical air moving systems, however, is typically discouraged in the general lighting industry primarily due to its inherent noise, cost and high maintenance needs. Accordingly, heat dissipation often becomes an important design consideration.
Further, LED-based luminaires are assembled from multiple components having different thermal expansion properties and typically rely on adhesive materials for affixing these components to each other. However, conventional adhesive materials may release gases during operation of the luminaire, compromising its performance. In addition, adhered components typically cannot be taken apart and must, therefore, be discarded together even when only one of the adhered components fails or needs to be replaced. Furthermore, different thermal expansion/contraction properties of individual components often constrain the design of the luminaire. Other drawbacks of known LED-based luminaires include lack of mounting and positioning flexibility, as well as undesirable shadows between individual fixtures when connected in linear arrays.
Thus, there exists a need in the art for a high-performance LED-based lighting apparatus with improved serviceability and manufacturability, as well as light extraction and heat dissipation properties. Particularly desirable is a linear LED-based fixture suitable for wall-washing and/or wall-grazing applications that would avoid shortcomings of known approaches.